Aim: To assess whether there is any association between membrane damaging toxin production by Staphylococcus spp. and self-reported TMD symptom expression in a group of patients selected to have CFS. Methods: Thirty-three defined Chronic Fatigue Syndrome (CFS) patients and 33 ageand sex-matched controls were assessed to evaluate the relationship between carriage of membrane damaging toxin producing staphylococcus, CFS and temporomandibular dysfunction (TMD) symptoms. Results: The CFS patients had an increased prevalence of face pain (Odds Ratio = 21.0, 95% CL 4.2-106, P < .001) and temporomandibular joint (TMJ) clicking/locking (OR = 5.7, 95% CL 1.423.5, P < .007), and the coagulase-negative staphylococcus maximum% B*-toxin haemolysis per patient. Both multivariate and univariate analyses revealed an association between the membrane damaging o*-toxin producing CoNS (MDT-CoNS) species per subject and face pain prevalence and intensity within both the CFS patients and the control subjects. No association was found between CoNS toxin production and TMJ clicking/locking. Importantly, áand B*-toxin production by CoNS was associated with patient reporting of arthritis. Conclusions: These data confirm the original observations of the association between MDTCoNS and facial muscle pain (Butt et al, 1998; McGregor et al, 2003). These data also suggest that MDT-CoNS associated facial muscle pain expression represents a distinct clinical entity, which has an increased prevalence in CFS patients.